I opened to #26251 to track the snowflake related changes. We wont' wait for them though before switching our macOS nightly builds to ESR 60. Thus, I'll disable snowflake for the time being in case it takes a bit longer to adapt it to the new toolchain.

The first pre-nightly Tor Browser based on ESR 60 finished building. Could someone with recent enough macOS systems test whether the bundle is at least running?

I did some quick tests on a Retina MacBook Pro (macOS 10.13.4) and on an
older iMac (macOS 10.11.6). Good news so far: the only problem I noticed that might not be
known yet is that the app icon was positioned incorrectly within the DMG installer window:

I am not sure what caused that problem, but we should fix it when we re-do that window to use the new icon.

The first pre-nightly Tor Browser based on ESR 60 finished building. Could someone with recent enough macOS systems test whether the bundle is at least running?

I did some quick tests on a Retina MacBook Pro (macOS 10.13.4) and on an
older iMac (macOS 10.11.6). Good news so far: the only problem I noticed that might not be
known yet is that the app icon was positioned incorrectly within the DMG installer window:

That's great news, thanks! I posted patches for all child bugs. I'll add patches for the remaining bugs on a branch for this ticket including all the other patches, too, in order to have one branch which one can actually use to test building the whole thing.

commit aabed936170b9ea88df2037e8d452dc5d9915f20 which installs xz-utils which we now need for MAR file generation and commit fcb2a3707af71bcd564bf0dd8a563835eeea6b9b which fixed a missing "TorBrowser.app" -> "Tor Browser.app" transition.